Flaw detector for electrical conductors



Jan. 3Q, 1934. E. A. SPERRY 3,944,954

.FLIAW DETECTOR FOR ELECTRICAL CONDUCTORS Original Filed Aug. 10, 1928ENTOR 80 R. A. SPERRYDECZ EDWARD Gv-SPERRY, sxzcuroe ELME 5 4M ATTORNEYPatented Jan. 30, 1934 FLAW DETECTOR FOR ELECTRICAL CONDUCTORS Elmer A.Sperry, deceased, late Brooklyn, N. Y., by Edward G. Sperry, executor,Brooklyn,

assignor to Sperry Products, Inc.,

{ Brooklyn, N. Y., a corporation of New York Original application August10, 1928, Serial No.

298,771. Divided and this application August 1, 1931. Serial No. 554,485

Claims. (01. 175-183) 5 and the like. This application is a division ofcopending application Serial No. 298,771, filed August 10, 1928, forFissure detector for metals. The method here employed comprises passinga current through the conductor to establish an electro-magnetic fieldsurrounding the same and to detect any variations in the axis of thecurrent caused by any of the imperfections noted above by means of apair of opposed detector coils designed to generate a diiferential E. M.F. whenever such flaw or imperfection is encountered.

The invention has particular applicability to the specific materialtested, namely, wires, cables or the like, and provides means wherebythe current through the conductor is automatically shut off as the endof the cable approaches the current supply brushes.

It is a further object of the invention to provid means whereby thecurrent brushes and the detector coils may be moved away from theconductor to an inefiective position as the end of the wire or cableapproaches the current brushes.

It is a further object of the invention to provide means forautomatically varying the current density through the conductorcorresponding to the speed of movement of the conductor relative to thedetector mechanism. I

It is a further object of the invention to provide means for measuringtheamount of conductor that has passed through the detecting mechanism.

Further objects and advantages of the invention will become apparent inthe following detailed description thereof.

In the accompanying drawing,

Fig. 1 is a diagram illustrating the method of fiaw detection employedin this invention.

Fig. 2 is a second diagram showing the simplest form of detecting meanswhich may be employed in this invention.

Fig. 3 is a side view, partly in diagrammatic form, of the invention asapplied to the testing of wire or cable in a rolling mill.

Fig. 4 is an end elevation of one of the main supply brushes andoperating mechanism therefor.

Fig. 5 is an end elevation of the apparatus looking in the direction ofthe arrow in Fig. 3.

Fig. 6 is a detail of one group of main supply brushes, certain of theparts being shown in section.

Referring first to Figs.'1 and 2, if a current is passed through the bar1 from generator G and the bar possesses no hidden flaws or fissures,the current will fiow uniformly therethrough and, therefore, a uniformmagnetic field will surround the bar. If, however, there is a fissure orblowhole at, say, point 2 in the bar, which lies near the top, the mainportion of the current will pass under the fissure as shown by the arrow3. This will, of course, produce a change in the magnetic fieldsurrounding the bar at that point, weakening the field above the bar. Ifthen the wire 4 of Fig. 2 or the coil or coils 6 and 7 of Fig. 1 aremoved relative to the bar near the surface thereof, the E. M. F. orcurrent induced in the same will be varied as point 2 is passed over,which variation may be utilized to give an indication of the flaw. Thisvariation may be amplified in any suitable manner at 4', such as bythermionic tubes to actuate a recorder or indicator 5', or the coils maybe connected to ear phones 5 which act both as an amplifier anddetector. It is preferable to employ a second coil 7. cross-connectedwith the coil 6 so as to balance out the eifect of variations in thephysical speed relatively between the coil and conductor and also anyvariations in voltage in the main supply current through the same. Inother words, if the amount of current flowing through the conductor orthe speed of travel varies materially, a change in E. M. F. would besimultaneously generated in each coil but since the two coils areopposed, this would balance out so that no indication would reach theamplifier, receiver or indicator.

The above system of flaw detection is more fully described and claimedin the said co-pending application, Serial No. 298,771, but the saidprinciple of detection is applied to the testing of metallic wire, cableor rod as shown in Figs. 3 to 6 inclusive, which form of invention isapplicable to thetesting of such conductors as they pass through therolling mills. The wire is shown at 50 and is represented as movingrapidly in the direction of the arrow between the rollers 51, 52.Current is supplied to the wire by the main brushes 53, 54. Between saidbrushes are placed a pair 'of spaced detector coils 55, 56, which, inthis instance, surround the wire to some predetermined extent. Said,coils are preferably split or open at one side together with thepermalloy .centers 5'], and are mounted on hinged frames 58, 59 so thatthey may be opened as shown in dotted lines in Fig. 5, the two framesbeing hinged at the point 60. Frames 58 and 59 are each provided withears 61, 62 extending beyond the pivot 60 and connected to a spring 63which normally tends to pull the ears together as shown in dotted linesin Fig. and thus open the coils. A pair of pivoted links 65, 65 areshown as hinged to ears 61, 62.,forming a pantograph. The outer end ofthe pantograph is shown as slidable in a .slotfil' in bracket 67 and isnormally held forreached as well as the detector coils.

wardly, as shown in Fig. 5 by trip 68, secured to a shaft 69. When saidtrip 68 is revolved upwardly as shown in dotted lines, the springimmediately opens the coils as shown in Fig. 5, thus releasing the wireand placing the coils where they will not be harmed by the loose end ofthe wire as it flies through the apparatus.

Resting on the wire at the right side of the apparatus is shown a wheel'70 which is revolved by the passage of the wire thereunder. Said wheelis shown as driving through suitable bevel gearing 71-, a shaft '72which operates through flexible shaft 72', a linear measuring device 78so that if a flaw is encountered the section of wire it lies in may bereadily located. Said shaft is also shown as operating a speed indicator'14. The wheel '70 is joumalled on a bell crank lever 75 pivoted onshaft 76. The upwardly extending arm 77 of the bell crank lever normallymakes contact with a switch 78. When, therefore, the wire passes fromunder the wheel '70 it drops down, moving arm 7'7 out from engagementwith switch 78. Switch '78 is in the main circuit of the supply brushesso that means are thus provided for opening the main supply current whenthe end of the wire is reached, thus preventing severe sparking at themain supply brushes.

Also, it is preferable to connect the speed indicator '74 with aresistance or other means for varying the amount of supply current. Itis advantageous to send as much current as possible through the wire andthis amount may, of course, be increased with the speed of the wire,since at high speed the wire will not have time to heat up and'may carrymany times the current it could carry if at rest. Means is thereforeprovided for increasing the current with the speed or, stated anotherway, for decreasing the current as the speed decreases, thus providingfor maximum operating eificiency under all conditions without the dangerof overheating the wire. To this end the speed indicator is shown asoperating a rheostat or variable resistance 40, the movable arm 41 inthe rheostat being connected to or actuated by the speed indicator, sowhen the speed is low a much less current is sent through the wire thanwhen the speed is great.

Preferably also means is provided to move the main supply brushes out ofthe path of the free end of the wire, when the end of the wire is Forthis purpose the main supply brushes are shown as mounted for sliding infour radial slots 80 in a supporting frame 81 so that the brushes may bemoved into or out of contact with the wire 50 (Fig. 4). Each brush has apin 82 thereon which connects to the slot adjacent the brush and bearson one portion of a four-part cam 83. When the cam is revolvedcounter-clockwise, i. e., in the direction of the arrow in Fig. 4, itwill readily be seen that all four brushes will be withdrawn fromcontact with the wire 50. The brushes are normally held against the wireby a continuous spring band 84 (see Fig. 6). The brushes are alsopreferably placed at a slightly difierent angle to the wire as shown.

ex-goo:

Said cam 83 is preferably revolved to withdraw the brushes by thedropping of the roller '70 as it reaches the end of the wire, whichoperation also performs the other functions described above. As shown, alink 85 is pivoted to the cam which is connected to the lever 86 pivotedat 87. The outer end of said cam is in turn connected to a link 88 whichis pivoted to bell crank lever 89. Said lever in turn is shown assecured to shaft 89' which is operated from shaft 76 through bevel gears'76. At its lower end, lever 89 also operates the bell crank lever 68 bya pin slot connection 90 so that the main supply brushes are withdrawnat the same time that the split coils are open to prevent damage to theapparatus.

In accordance with the provisions of the patent statutes, the principleand operation of the invention has been described, together with theapparatus which is now considered to represent the best embodimentthereof, but it is desired to have it understood that the apparatusshown is only illustrative and that the invention can be carried out byother means. Also, while it is designed to use the various features andelements in the combination and relations described, some of these maybe altered and others omitted without interfering with the more generalresults outlined, and the invention extends to such use.

Having described the invention, what is claimed and desired to besecured by Letters Patent is:

1. An apparatus for detecting defects in electrical conductors such aswire, cables, bars and the like, said conductor being adapted to be fedthrough the apparatus, comprising means for passing an electric currentbetween spaced points as the conductor passes through the apparatus, aflaw-responsive means positioned adjacent said conductor between saidpoints of current introduction, and means controlled by the approach ofthe end of said conductor to said apparatus for moving said flawresponsive means away from the conductor.

2. In an apparatus for detecting hidden defects in electrical conductorssuch as wire, cables, bars, and the like, said conductor being adaptedto be fed through the apparatus, means for supplying electric current tothe conductor as it passes through the apparatus, a flaw-responsivemeans adjacent said conductor, and means controlled by the rate of feedof said conductor for varying the amount of current supplied to theconductor in predetermined proportion to the said rate of feed.

3. In an apparatus for detecting defects in electrical conductors suchas wire, cables, bars and the like, said conductor being adapted to befed through the apparatus, a plurality of spaced brushes for supplyingcurrent to the conductor, means for moving said brushes into and out ofcontact with the conductor, a split test coil normally surrounding saidconductor, and means for opening and closing the said split coil.

4. An apparatus for detecting defects in electrical conductors such aswire, cables, bars and the like, said conductor being adapted to be fedthrough the apparatus, comprising means including a plurality of currentbrushes for passing an electric current between spaced points as theconductor passes through the apparatus, a flaw responsive meanspositioned adjacent said conductor between said points of currentintroduction, and means controlled by the approach of the end or saidconductor to said apparatus for moving said current brushes away fromthe conductor.

5. An apparatus for detecting defects in electrical conductors such aswire, cables, bars and the like, saidconductor being adapted to be fedthrough the apparatus, comprising means including a plurality of currentbrushes for passing anelectric current between spaced points as theconductor passes through the apparatus, a flaw responsive meanspositioned adjacent said con-

